Automatic telephone system.



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AUTOIAA'HCTELPHON'E SYSTEM. Hummm msn Au-s.25'. e914.

Pafgented Sept. 3, i915,

3 SHEETShSHEET l.

B. D. WILLIS.

AUTMATIC TELEPHONE SYSTEM,

APPLICATION FILED AUG-251914. v

Patented Sept. 3, 1918.

3 SHEETSSHEET 2.'

Y. no stra ns .are

OFFICE.

BERNARD D. WILLIS, F CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, .A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM nemers.

Specification of Letters Patent.

Patented Sept. 3, 1918.

Application filed August 25,1914. Serial No. 858.480.

T'To alt .whom t may concern Be 1t known that I, BERNARD D. WILLIS, ia citizen of the'United States of y.-\merica,

i 'fand resident of Chicago, 'in the county nt' 5 Cook and Sta-te of Illinois, have invented "certain new and useful Improvements in Automatic Telephone Systems, ot which the `'following is a specitication.

My invention relates to improvements in automatic telephone-systems. audmore p/articularl to what is known as district sys# temst iatis, systems in which main and branch exchanges are employed.

' The objects of my invention are to increase the trunkingtv elticiency trom the branch exchange to the main exchange by enabling' toll calls,.trouble calls and other calls in which it is desired to obtain connection with an operator to be extended over the regular trunks, instead ot' necessitating the employment of special trunks for tl purpose, yais-has heretofore been customary. By my invention it is necessary to employ but one 4set of trunks extending from the i branch exchange to the mani exchange. and

all calls can be made over these trunks.

These and other objects of' my invention will be more readily understood b v reference to the accompanying drawings, in which I SO'have illustrated one embodiment of my invention in connection with automatic' switches ot well known types. i Figures 1 and 2 show a complete connection in a branch oil-'ice ot an automatic telc- 85 phone system embodyinplr the principles ot in v invention.

Fig'. 3 shows part ot' the equipment at the main oilice.

It has heretofore been customary `in a 40 small branch otlice to have several groups ot special service trunks to the main otlice in addition to the. regular outgoing trunks. For instance, it has been necessary to provide a` special group of trunks for long'dis- I tance calls` t'or trouble calls, tor interinacalls ot the above-mentioned character will be. sent in to the main otlice over the regular out-going trunks. Vi'e will assume that the.

regular outgoing' trunks to the main ottice are accessible t'rom the third level of the hrst 56 selectors in the, branch otlice, and these outgoing trunks terminate in the main otlice in incoming second selectors. As is well known` the trunks in the tenth gir 0 level of the rst selectors ot' the main Ioltice lead to the recording section oft-the toll board, and in the system disclosed herein it. is assumed that the trunks in` they sixth level of the. special selectors E are multipled with the corresponding trunks in the 0 level of the. rst selectors.

lVhen a subscriber at the branch oliice., the subscriber A, tor example, desires to 4call long distance. he removes his receiver and calls the digit (l. The removal of the receiver causes the line switch C lo extend the connection to lthe tirst. selec-tor E. The selector E. upon responding to the impulses for the digit 0, extends the connection to the impulse-sending machine F. The iinpulse machine F thereupon `causes a line switch (not shown, but which is in the saine group as the line switch C) to seize a selector (not shown. but which is in the. saine group as the lirst selector E). whereupon the impulse machine li` delivers three impulses to the, tirst selector (not shown), which causes it. to obtain connection with the repeater li. which is associated with a. trunk leading to the incoming' second selector E. The impulse machine l*` now delivers three impulses to the incoming second selector E?. which causes itl to extend the connection to the special selector E3. A further set of six impulses from the impulse machine F causes the. special selector E3 to make connection with the 'answering jack equipment J which is located at the recording position on thel toll board. In this way a subscriber in the branch exchange is put in connection with the ltoll operator by the simple operation on his part ot calling the digit. 0. At the. same timeI it willbe seen that the connect-ion is extended over the regular outgoing trunks to the niain office. rlhc remaining calls of th above-mentioncd character are made n' a manner similar to that of the long distance call, except that the impulses delivered by the impulse machine will be for different digits.

The automatic substation A (Fig. l) coinprises the usual receiver 2, transmitter 3, ringer Je and condenser 5. Being an automaticl substation it is also provided with a suitable call-sending mechanism for controlling the automatic. switches, which mechaing '12, i line rindingr nisin is represented diagrammaticay by c. pair of impulse springs G und 7 and an im- 'pulse 'Wheel 8, which latter may be controlied by a dial provided with ng ,if holes in such a Way that the impulse springs may be. momentarily Separated t number of times corrcoponcling to the respective, digits of' the nnn'ilner of the called subscriber.

The subscriber@ individuni Switch i (Fig. l) is of the general type of subscribers Switch Shown in British patent to R. W. James Notll of 1906, being. lioiveer, oit the particular type tliselof-:ezi in Britieh patent to T. G. Martin No. M19 oit E i. This line switch comprises among other tie tailS a plunger (not shown) attached to 'the enti ot' n so-ealieil ijilunger arm 9 Wiiic is controlled h' the muguet TLG. The magnet conun'i,-';.e"A tour wintliuga. namely, a. puiL tlowu Winding il. n cut-ott or holding w".

till anti` an auxiliar winding' li. 'The core o i the nuignct it) i s ei'uritrueteifl that 'the magneti(- eircnit ofi; the u'iiulinga ll. anti E2 separate troni that. ot

the uii'ielinga ifi zu d A. This muguet. controlsI 'the cutoti? armature '15. The puik in ".vi'ndin.11- ll. operates hoth the plunger arm il) and the zirrnutine 153. while the cutoff or holding' whirling l2 is tfzong enough only to aporta the @ut-yt urnniture 1 5 nntlhoifi ilrf phmg'rr erin in opeuted pont-ion, n the piung'er atri if; torecil into a brink i' t-(nitact. Springs. forearm the Springs liti, i' FSE and 'i9 'urto fuigjagezneut with the .1. 31. 22 anni, 2.9; 'reniiertivoly. ftln only one set olf ai -i urs (16 to 523, in-

clit-sivo) is Shown. each line switch is 'pro ruled, with n plurmiy ot auch et s, ouch. Het forming; the termi iii uit u trunk line lending; tu a aelector .mitch Each runt-i iinc connetted in niuhipie with the corresponding Uhe group which ie rourulletl hy 'the niaeter switci.

'f is: gontrolled ov the. subs through the medium oit the line winding lf; new; wil? hereinafter he more tuliy exp tuned.

inns-tm; mi'ich (Fig. l) i# of the anni@ grt-neral type ae that iliaclosetl. in 'Brit i li pnteut to li. Vf. James 213.51591 19ML ihore reiferrcil to. heirl'. ho\\e\'er. t the mrtieulur type tlhscloseil in .finiti .i itiaii ia'enf to T. (i. Martin No. ivf-i1?) ot tutti.

i netion of the u'iaHter Switch. un ia' il lmou'n. is to maintain the pluugrerwir' .ril it line aufiichos in po, l.ion

ur iille trunk the terminal et an 'iilie trunk line. xf'toi' switrh it) (Fig. li ir: oi; the

il )e ot aelector Switch ilisi'lo'otl iu 'uiteii' tiatefa Letters Patent No. tllirnl. granted 'iareh lli. 190i?. to Keith. iilririteon :intl ilriizlffoint-Xrep?, hut tlu` Howaiieii iaitawitrh i5 omitted. unil the ein-nits are inoffi- :l to :uiupt the `Snitch to operate in n .ioni ir. vwhich thc contini otiiee :apparatus xcancifoiieffi 'oy inipuiseei tleiiicrtii over the two sides ofthe tino in f noun 1i. British patent to T. tv :ntin No. 111.5516 ot HB2. Among other details the selector E comprises a bank oitcontacts arranged in horizontal rows or levels, which contacts are adapted. to be engaged by a set of Wipers 2%, 25 and 26 carried upon a shaft (not shown) which has e. vertical n'iovement controlledby the vertical magnet and .a rotar)v movement. controlled by the rotary'mngnet E28. The operations ci the furious parts ot the switch ure controlled through the nie- 'tliinn of the double-wound line relay 529. tienne 'tor permitting the Switch to he re- Storefl Le norniai position are provided in the release nmg'net $30, which, upon energia ing. witlrt'taws the retaining pawls from the Shaft. when the switch. shaft imS been raised one or more Steps from lowest. position. The rciaya and B- arc Ialoiv acting-that is, :slow to release. their armatures upon deer zing. The ueieetors E2 and E3 :irc Similar 1nv all respects to the selector E.

fiicconnectorswitch ii (Fig. 2) is of the The Springe 31 and E59. close only' shown) which hue a` Vertical movement contruite-1i ln' the vertical magnet tantl a rotary nurreuunt eimlrolleii by the rotary magnet. 35i. vilul usual `aille switch compri ing the u'iper,-: l0. -l-t, 'l2 and 13 is controlled by the privatiy nsagljnet it in the usual antl r.'cli-i-:no\fn imnnur. The operutions ot' thc various; parts of the uniti-h arc controlled through the n'u'iliiun ot the douliie-i'ouul Eine. relay iti. uniti reluy livingnonnertml 'with the line through thc reversing springs of a suufuiieii inuit-litige relay l). throng@ the u intiinga oi? which latiei relay the m llefl luie 1e prox' with talkingn current. The r rela' nti'orils the menus hy which 'rentrent se: ipplieil. to tho ralicd line. i'orpesinii tingy the su'il clito he restored to normal i* .i ion ure providedinthe release .mguet 1lb. which. upon energizing. wit-htuxv the retaining pawls` ironl the shat'i. i;r '55.* :nul Si? close onlyY "when the, a'ui'i'oh shall' hun heen raisril oiie o." nuuo #tenu 'from its owest position. The reiays 3,! :nul 5; :ire k#low :loting-that is. sion' to rele-.uae their armaturesy upon L'leiinergriyling.

The repeater i( has a line, rehry a. Slow :.uatinir rig-lm; 54 and a battery`V` Levi/,eve

reversing relay 55. The line relay 53 is normally bridged across the trunk extending tothe repeater from the third level of the banks of the rst selectors, and is so arranged that when its armature operates in accordance with the impulses Atroni an impulse-sending machine or calling device, it opens and closes the bridge across the trunk extending to the selector E2 a correspond ing number of times. Among the functions of this repeater switch is to receive impulses transmitted by the impulse-sending machine or calling device and repeat them to the switches farther on. Furthermore, it supplies battery current to the calling line and maintains a holding circuit for kthe switches in front of it, without requiring a third conductor to be included in the trunk line extending to the switches beyond.

i The impulse-sending machine F (Fig. v1) consists ot' a constantly rot-ating shaft upon which are mounted a pair of impulse cams P and P.` Associated with these impulse cams there .may be a number of groups of relays similar to the group shown at F. The function of each of these groups ofrelays is to supply battery current to the calling line and maintain a holding circuit for the switches in front, of it. At the same time means are provided by which a series ot impulses corresponding to the notches upon the. cam' P are sent out to advance the switches ahead to the desired point.

The impulse-sending machine F is the same in general principle as the machine F.

The walled substation A (Fig. 2) and its individual line switch (1 is similar in all respects to the calling substation A and its individual line'switch C.

For the purpose oiu supplying battery'current for -operating the apparatus and for talking purposes, there are shown the batteries B and B, each having one terminal grounded at G. For the purpose of supplying ringing current there is shown the ringing current generator R. The busy signaling machine Q, as represented herein, comprises an induction coil or transformer, vthe primary winding ot which is included in a local circuit with a battery and an interrupter ot' high frequency. Through the medium of this interruptor an interrupted current. is supplied to the primary winding,

which induces an alternating current in the secondary'. winding, whereby, when said winding is connected with the subscriber-s line, a. buzzing sound is heard in the vreceiver.

A general description ot the. apparatus having been given, ity will now be explained how connection can be established between the line Aof substation A and the line of sub station A. Thel number of the called substation will bel assumed to 222. Since the automatic switching apparatus disclosed herein is in general well known in the art, and is described in the publications .herein referred to, its operation will be. explained in a more or less general manner.

iVhen thesubscriber at substationv Aigremoves his receiver from the switch hook preparatory to making a call, an energizing circuit is. closed through the line winding 13 of the line 'switch C. The armaturetyf i upon being` operated, due to the energizing of the winding 13, closes a circuit through:

the pull-in winding 11. The pull-inv wind-y ing 11 upon energizing, attracts both thearmature 15`aiid the plunger arm 9. The plun- 'ger arm 9, upon being attracted, forces the plunger which is attached to the end thereof into the bank of trunk terminals to which it has access, forcing the springs 16, 17, 1S

Land 19 into engagement with the springs 20, 21, 22 and 23, respectively. The engagenient of the springs 16 and 19 with the springs 20 and 23, respectively, closes a circuit through the line relay 29 of the first selector E. The relay 29, upon energizing, closes a circuit through the relay 33. The relay 33 in turn, upon energizing, aifords a holding circuit 'for the holding Winding`12 of the line switch C, and also places a guard-` ing ground potential upon the connector private bank contact associatedwith the line switch C. This circuit through the holding winding 12 is closed beforetlie armature 56 falls back after the circuit through t-he line winding 12 -is broken by the attraction of the armature 15. The armature 56'does not fall back immediately upon the attraction of `the armature 15, due to the fact that simul called number, whereby the substation im-V pulse springs are separated twice momentarily, each time breaking the circuit of the `line relay 29 of the selector E; The relay of the selector being slow acting does not deiinergize during the momentary interruptions of its circuit by the relay 29, and consequently each time the latter relay denergized,an impulse is transmitted through the vertical magnet 27. The vertical magnet rceeives two impulses and-operates to raise the switch shaft and wipers two steps to a po- Sition opposite the second row or level ot bank contacts, and atthe same time the shaft-controlled. contacts 31 and 32 are closed. The Slow acting relay 84 is maintained in its energized position continuonsly while impulses are being transmitted to the vertical magnetfthrough it.. and in its energized position closes a circuit through the relay 58. The relay 58, upon energizing, il'orms a locking circuit. for itself. Thus, upon the deenergizatitni oli' the relay il after the .last impulse han been delivered to the vertical magnet., the. relay 5S reniaii'is energized and the circuit of the rotary magnet 2S in elosed` The rotary magnet, upon energizing'. rotates the shaft wipers one step, and by opening the springs 5S) and (St) breakl its own circuit and the circuit olf the relay 5h. lil' 'the first trunk line of the. aecond level is idle, the relay 55% deenergien` as soon as the Springe` t3() are opened. lt this trunk line is buey` however. the private wiper :25 linda the contact which it engages provided with a guarding ground potential which is transmitted to the rela)v thereby prevent ingr it from deinergiaino. The rotary male'- net, however. denercif/iea when the springe: 59 are opened.y regardless ot' whether the relay 5S remains energized or not. lt' the relay ata remains enerc'ied, the circuit ol the rotary magnet will be again cloned an soon as its artnz'tture. drops baci; tar enough to close the springs an and titl. The rotary magrnet will, therefore. operate in a manner laimilar to that oi" a buzzer to advance, the wipers step by Step over the contactantntil the nongrounded contact oi' an idle trunk line is reached by the wiper 25, whereupon the re lay 5o deenergrizes. The relay 5S, upon de energizing` whether ai't'er one or laereral operations oii the rotary magnet, permal'iently breaks the circuitoi` the -Said rotary magnet` and clones the circuit ot' the switching: relay til. 'lho relay (il, upon energizing. discon net-ts the, line relay z5) from the line and ere tends the line connection overthe henry cov ductorw` shown through to the connector t the connector thereupon and closes the circuit. of the relay 51. which in turn, upon energizing, completen' a holding' eireuit for the relay 1 of the selector ll and for the windingr 'l2 of the line switch C. This circuit maintains the Said relay and winding energized after their original energizing circuit is broken by the relay 3?, which denergizes shortly after the line relay 2t) is disooi'niected from the. line.

The calling subscriber now opel-ateaI his callingl device for the Second digit 2 oi. the called ninnber, whereby the substation iinpulse springs are separated twice momentarily, each time breaking the oircuit ofthe line relay 46 oli the connector H. 'lhe re' lay 51 of the connector being slew aetinp; does not denergize during the momentary interruptions of its circuit by 'the relay 46, and consequently,each time the latter ref line. rela): iti of the wiper` 2i and itl becomes enerwized .lay denergizes, an impulse is transmitted through the, vertical magnet. 'lhe vertical magnet receives two impulses: and operates to raise the switch shaft and wipers two Steps to a position opposite the Second row or level of bank contacts, and at the saine time the Shaft-controlled Springs 49 and 50 are closed. The Slow acting relay 52 is maintained in its energized position con tinnously while impulses are being transmitted to the Vertical magnet through it', and in its energized position clones a circuitl through the prirate magnet eli, Thin circuit is broken when the relay 52 denergizes after the last impulse has been delivered to the Vertical magnet. the breaking of said circuit causing the private magnet ll to deenergg'ize` thus permitting; the aide Aswitch to paw to Vzet-ond position. ln parisino' from tiret to second position the side switch wiper lll transfers the battery conneetion from the vertical mag-net 38 to the rotary inagnet 39.

The calling subscriber now operates hin` railing` device for the laat` digit Q. in response to which the connector line relay operates to transmit two impulsenI through the rotary magnet Si), whereb). the shaft wipers are ro tated onto the contacta` at the desired line.. The relay 5:2 operates in response to the iinpulaes ior thin digit in the saine manner as for the previene` digit to canne the private magnet Yl-t to advance the side Switch to third position. lSy the engagement ol the side Switch wipers ll and l2 with their third-position contactv points. the line connection is completed with the called line. wUpon the etrg'agfjenient of the side switch wiper lil with it, third-position contant point. a circuit completed through theV ct1t.-oit' wiinlingj of the line. switch t". rlhe cutoff' winding ot the line, awi'toh' C, upon energizing. dixconnects the line relay from the called line. The connection of' ground with the connector private baul; Contact associated with the relied line prevents the called line from being; seized by nome other connector Switch. By the engagement of the aide awitol. wiper 40 with its third-position Contact point, the circuit of the ringer relay i? is closed. The ringer relay is energized intermittently due to the interruptor (3:2 and operates to disconnect the Calling 'line from the called line and to bridge the ringing; current generator R across; the 'called line to signal the called subscriber. Upon the response of the called subscriber his line i5v provided with talking current through 'the windings of the back-bridge relay i-5, which relay, upon energizing, closes the circuit of thev ringer Cut-oil' relay G3. The ringer cutotl' relay` upon energizing, interrupts the eireuit ot the ringer relay L17 and closes .a locking circuit for itself independent of the relay 45. Furthermore, the baolebridge re-` l ing,

' shaft and its N lay 415 upon. energizing, operates to reverse ne direction of the flow of current in the calling line.

Upon the completion of the conversation, the restoring of thereceiver causes the circuit of the line relay 46 of the connector H to be opened. The relay 46, upon denergiz# opens the circuit of the relay 51, which in turn, upon denergizing, removes the holding ground from the relay 61` of the selector E and from the winding 12 of the lipe switch C, and in addition closes the circuit oi the release magnet 4S. The release magnet 48, upon energizing, operaties to withdraw the retaining pawls from the shaft and its own circuit is opened at the springs 49 when the said shaft reaches its lowest position. The relay G1, upon kdeenergizin'g,

fcloses the circuit of the release magnet'SO.

The release magnet 30, upon energizing, withdraws the retainingr pawls from' the own circuit is broken@ at the springs L'31 when the said shaft reaches its lowest position. rlhe winding 12, upon deenergizing, releases the armature 15 and the plunger arm 9, thus allowing the line switch C to return to normal position.

It having been explained how one subscriber establishes connectionr and releases the saine, itwill now be explained how a connection is prevented from being made with a busy line. It' the called number is busy, there will be a guarding potential upon the connector private bank contact associated with that line, just as explained v in connection with the line switch C.` The connector private wiper 36,'upon engaging this guarded Contact and before the side switch has passed to third position, completes an energizing circuit through the relay 64 in series with the private magnet 44. rllhe relay 64, upon energizing, opens the circuit of the rotary magnet 39, and at the saine time connects the busy tone from the busy machine Q with the calling line. In addition, the relay (34V upon energizing, orins a locking circuit for itself through the oiif-iioriinil springs 50. sciiber, upon hearing the busy tone, restores his receiver to the switch hook and the release oi' the apparatus follows in practically the same manner as previously explained.

lft will now be explained how a subscriber at the substation A may obtain connection with a toll operator, the directory number oi'* whom. is 0.

Vl/'heu the. receiver is removed at the sube station A, the line switch C operates to extend the connection to the selector E. Upon the calling subscriber operating his calling dwxice ior the digit 0, the wipers of the selector arev brought to restupon the iirst .lill e trunk in the tenth level or' its bank, which trunk we will assume leads to the impulse i'nacliine F. A circuit may now bef-jtracedV The [calling sub-j prepared.

from ground G1 through the upper 'winding of the line relay 65, bank contact 66, line wiper 26 to and through the substation A, line wiper 24, lbank contact 67 and the lower winding of the line relay to battery B. Upon the energization of the line relay 65, a circuitis formed from-ground G2 through the springs 68, springs 69 and the relay 70 to battery B. Therelay 70, upon energizing, forms a locking circuit for itself from ground Grthrough the springs 71 and 72, springs 73, springs 74 and the relay 70 to battery B. At the 'time the relay 65 ener-A gizes, another circuit is formed from ground G2 through the springs 75 and the relay 76 to battery B. The relay 7 6 is 'slower to encrgize than the relay 70, otherwise the relay 76 would open the circuit of the relay '70 before said relay. had formed its locking circuit. The energization of thelrelay 76 supplies a holding circuit for the relay `61 of the selector E and for the winding 12 of the line switch C. The said circuit may be traced from ground G4 through the springs-77,`

after, the

(not shown) which is similar to the line i .switch C andis in the saineffgroup. When the relay 7 O is energized, a bridge is formed which causes the said line switch to be. operated and extend the connection to a selector (not shown) which is similarljin all respects to the selector E. When the point 79 on the cam Pf rengages the spring 71 it causes thel 'said spring to breakfroin the spring 72. A circuit may now be traced from ground G3 through. the springs 71 and 81, relay S2, springs 74 and the relay'70 tobattery B.' The relay 82, upon energizing, opens the-,springs 7,3, so that when the springs 71 and 72 again come into contact, the relay 82 will not be again shunted out. And in addition, by the closure of the springs 83, the circuit for the impulse .relay Le is Each time a* projection .on the cani P forces the springs 85 into engagement, 'a circuit niay be traced lfrom groun through the springs 8.3, relay 84, springs 85 and the resistance 86 to battery B. Each vacross the trunk lconductors 133 and 134 alsa time the relay 84'energizes it opens the bridge across the trunk conductors 133 and.

134 and in this way delivers an impulse over the trunk. The three impulses caused by the first group of' projections upon the cam P .in that level is selected, which vwe will .as-

sume leads to the repeater K. The thi pulses delivered by the next group jections upon the cam P cause the lint .-.eia

53 of the repeater K to transmit three impulses over the trunk conductors 125 and 126 to the line relay 87 of the select/or E2, whereupon the wipers ot the selector come to rest. upon the first idle trunk in the third level of its bank, which we Will assuine leads to the selector E3. The six impulses caused by the next group ot projections upon the cani P cause the line relay ot' the repeater K to transmit six inipulses to the line relay 88 of the selector l?, whereupon the Wipers of the selector KE3 come to rest upon the first idle trunk in the sixth level of its bank, which We will assume leads to the jack equipment J. After the last group ont projections on the cam l) has passed under the springs 85, the depression 8O on the cam P passes under the spring "il and thereby opens the springs 7l and Si. The relay-82 being slow acting does not deenergize immediately, but the relay 7U deenergize's and thereby bridges 'the coil 8l) across the trunk conductors 133 and 134:. The impulse-sending machine is now in readiness to extend connecti n between any other group or groups of .relays associated with the said machine (not shown) and the operator at the main exchange. lpcn the connection being' exten( lo the answering jack equipment el', the relay S10 becomes ener gized and in x doing ali'ords a holding ground .tor the switches in front thereof. At the same time the relay closes a circuit through the signal lamp 91. |lhe operator, upon seeing' the lamp 91 lighted, operates the hey K2 to cut her talking set (not shown) across the calling' line, whereby she may converse with the calling subscriber. It will be seen that with the key K2 operated, an Iadditional holdingground is supplied to the switches preceding the ansiver ing jack equipment J for the reason that the apparatus will not be released should .the calling subscriber hang up before the operator has restored the key K2. Upon the completion of the conversation, vthe operator restores the hey K2; The hanging up of the receiver at the calling' substation will then bring about the release of the apparatus in a manner similar to that already explained.

When the telephone has been taken out of service it is desi able that any one calling that line be automatically connected with an operator who can then give the information necessary for obtaining connection with the called party. Assuming` that` the telephone the number of which is 224 has been removed and that that line has been connected in multiple with several others to the impulse machine F. rlhen When a subscriber in the branch oilice calls that num-l ber, and the side switch el the connector i H steps to third position, a circuit may be traced from ground GG through lthe lefthand winding of the relay a5, springs 92, springs 9i and 95, line Wiper 37, bank con tact Se, relay 97, coil 98, bank contact 99, line wiper 35, springs and 10i, springs 93 and the right-hand WindingI of the relay i5 to battery l. The relay #i5 will not energine over this circuit on account of 'the high resistance coil 9S. rilhe relay 97 will ener`4 gize, however, and in so doing Will close a circuit from grouiufl Gthrough the springs 1.02 and the relay 103 to battery B. At the saine time a circuit will be closed from ground GT through the springs i092, springs 105 and the relay 10G to buttery lll. 'lt will be seen that at the instant between the pulling up ot the relay 9'? and the pulling;` up ci the re- 103, the high resistance coil. 98 and the relay 97 `will be short-circuited by means of the springs l0? and 108. This shert-circuit ing ofthe coil QS and the relay 97 Will allow sutlicient current to flow through the 'bach-bridge relay l5 to operatively energize it for an instant. This .will be long enough ferit to close the circuit throughthe ringer cut-oil relay 63, but not long enough for the reversal of the current in the calling line to operate a meter therein should there be one. Should the ringer relay 47 be energized when the side switch lirst steps to third position, the relay 97 will not energize, for. bein;r slow acting'. it is not affected by the ringing current. The instant between the energization oi the relay 97 and the energization oi. the relay 103 is sutlicient time for the relay 1.06 to energize, which7 upon energizing. forms a locking' circuit for itself in the same manner as previously explained in connection with the machine F. The trunk conductors 135 and 136 'terminate in a line switch in the same manner as eztplained in connection with the machine F, and the. subsequent operation of the machine ll" is the s'ame as explained in connec1 tion with the machine F, except that it produces impulses corresponding to the digits Sp-3%, which cause`the connection to be extended to an answering jack equipment before an operator detailed to take care `ot suc-h calls. v

It there should be any unused levels in the first selector E, the bank contacts of this level Would be connected with ggoups of relays (not shown) similar to the group of relays and the impulse machine F, and the operation of the same is similar to the operation of the relays and the impulse machine ll hereinbeiiore described.

lt will thus be seen that l have devised a very eliicient trunking arrangement between the branch and inain office by which it is necessary to employ but a single group of trunks. These trunks can be employed to extend connection to automatic switches i i e! whose operations are eonti'olled from the calling line, or these Same trunks can be employed for the purpose of extending connection to an operators board, such as a trouble operator or a toll operator, such connection being controlled by the automatic impulse sender at the central oflice.

While I have illustrated and described my invention in connection with automatic switches of well-known types, `it will, of course, be understood that different forms of switches could be employed without departing from the scope of my invention, and that various other` changes and modifications will readily suggest themselves to those skilled in the art.

What claim as vmy invention is:-

1, In a telephone system, a subscribers line, a trunk line, a plurality of automatic switches, an impulse transmitter on the subscribers line for transmitting impulses over said trunk to control the operation of said switches, an automatic impulse transmitter at the exchange, and means Jfor connecting said automatic impulse transmitter with` said trunk to transinitaimpulses thereover to control the operation of saidv switches.

2. In a telephone system, a subscribers line, a trunk line, a plurality of automatic switches, an impulse transmitter on the subscribers line for transmitting impulses over said trunk to control the ope-ration of said switches, an automaticimpulse transmitter at the exchange, and means controlled from the subscribers line Jfor connecting said automatic impulse transmitter with said trunk to transmit impulses thereoverto con.- trol the operation oi'r' said switches.

3. ln a telephone system, a group of trunks, an automatic selector switch, means for operating said switch to select any one l et of said trunks, an automatic impulse trans mitter, means for operating said selector lsiwitch to establish connection with said impulse transmitter, and an automatic switch controlled by said -impulse transmitter for selecting any one of the same group of trunks.

fi. ln a telephone system, a main exchange, a branch exchange, a group of trunk lilies ,extending betiveeii said exchanges, means for seizing one or' said trunks, a progressively movable wiper at the main exchange individual to each trunk lineLa plurality of automatic switches at said main exchange for establishing a connection with a Calledy subscribers line, a manual toll operators board lat the main'exchange, and Awmeans for establishing a connection with any one of said automatic switches, or witlisaid toll operators board, over any one of said trunk lines through the medium of one of'said wipers. k f

5. ln a telephone system` a trunk line, an

automatic Vimpulse-transmitting device, a

calling subscribers line, ineansfoi establishlishing a connection freil l line to said .impalec-transmitting device,

means controlled by the operation ofl sai n device for transmitting a plurality of seri of impulses over said trunk line, automatic l switches responsive to said impulses,v an inipulse-transmitter on the calling linmfmeans for connecting said trunkline with thecalling line so that a plurality; of operations of said impulse transmitter transmits a plurality of series of impulses over said trunk, and automatic switches responsive thereto 'for extending connection to a called line.

47. In a telephone system, a mainexchange,4 a branch exchange, a group of trunk lines extending between said excliaiiges,ynieans for seizing anyone or' said trunksa progressively movable wiper individua-ite each trunk, means for moving saidy wiper after the trunk is seized for extending regular calls over one oli said trunlis, and means for extending toll calls and trouble calls over the same group of trunks through the ine dium of one of said. wipers.

' S. ln an automatic telephone system, a plui'ality of lines each having for the purpose of being called, a particular numerical ldesignation consisting of a series of digits, automatic switches responsive to-impulses corresponding to the various digit combinations for connecting calling and called lines, and a call sending device accessible to calling` lines, said device adapted to transmit, each time it is seized by a. calling line switch, controlling impulses corresponding to the num-110 maining digits to operate the remaining switches of the series.- K

1 0. In an automatic telephone system, subscribers lines terminating in a -central exchange, a trunk line accessible to calling subscribers lines' through the medium of a Acalling subscribers line,I ipeaiis for estab; :1 5

Asaid subscribers series of automatic switches in response to the calling of a particular series ot' digits, a second trunk line haring access to the irst switch of said series, a call sender associated therewith and permanently adjust cd to send. impulses corresponding to the digits ot' said particular series cach time it 's operated, and automatic means accessible to calling lines :tor connecting with said second trunk line.

ll. In an automatic telephone system, subscribers lines terminating in a central exchange, a trunk line accessible to calling subscribers lines through the medium of a series of automatic switches in response to the calling `of a particular series of digits, a second trunk line having access to the first switch of said'series, a call sender associated therewith and permanently adjusted to send impulses corresponding to the digits of said particular series each time itis opeijated, and automatic means responsive to impulses corresponding to a single digit for connecting a calling line with said second trunk line and for initiating the operation of the call sender associated therewith.

12. In an automatic telephone system, a substation and a line therefor, a selector switch accessible to said line, a trunk line accessible to said switch, a second trunk line extending to an operators position, means comprising a series of impulse controlled` switches for extending connection from said first trunk line to said second trunk line,

and a calling device associated with said first trunk line adapted when the said rst trunk line is seized by said selector switch to send the necessary impulses to operate said series of switches.

13. In an automatic telephone system, a substation and a line therefor, a trunk line,

Aautomatic means for connecting said line with said trunk line, a second trunk line eX- tending to an operators position, means domprising a series 'of automatic directively controlled switches for extending connec-` tion from said iirst trunk line to said second trunk line, and an automatic controlling device associated with said irst trunk line adapted when. the said line and first trunk line are connected to control the operation of Said series of switches whereby the connection may be automatically extended to .the operators position.

14. In an automatic telephone system, subscribers lines, an operatofs position accessi ble to calling lines through the medium of a plurality oi automatic switches, and an automatic call sending equipment accessible to calling lines, lsaid equipment provided with means adapted to automatically transmit the necessary impulses to operato said plurality of switches.

15. In an automatic telephone system, sublscriloers" lines, an operators position ordileraars narihv accessible to calling subscribers lines may be extended to the operators position.

1G. In a telephone. system, au automatic switch, a trunk line, accessible to said switch, an impulse transmitter and another automatic switch associated with said trunk line, means for operating said lirst. switch to seize said trunk line, and means controlled by said impulse transmitter tor operating said second switch.

17. In a telephone. systei'n, an automatic switch, a trunk line accessible to said switch, an impulse transmitter and another automatie switch associated with said trunk line, means for operating said first switch to seize said trunk line, said impulse transmitter automatically controlled by the seizure of said trunk line to ope'ate said other automatic switch.

18. In a telephone system, an automatic switch, a plurality of trunk lines accessible to said switch, an automatic switch for each trunk line, an impulse transmitter common to said trunk lilies, means tor operating said irst switch to seize any one ot said trunk lines, and means controlied by said impulse transmitter for controlling the automatic switch associated with the seized trunh line.

19. In a telephone system, an automatic switch, a plurality of trunk lines accessible to said switch, an automatic switch for each trunk line, an impulse transmitter common to said trunk lines, means for operating said irst switch to seize any one of said trunk lines, said impulse transmitter automatically controlled by the seizure of said trunk line to operate the automatic switch associated with the seized trunk line.

20. In a telephone system, an automatic switch, a trunk line accessible to said switch, a rotary impulse transinitter and another autoi'natic switch associated with said trunk line, means for operating said .first switch to seize said trunk line, and means controlled by said impulse transmitter for operating said second switch.

2l. In a telephone system, an automatic Laatste for operating said iirst automatic switch to seize said trunk line, and means controlled by said second impulse transmitter for operating said second autpignatic switch when the trunk is seized. f

23. In telephone system, a callin@ line, an

impulse utransmitter associated therewith,`

an automatic switch, meansv for connectin said line with said automatic switch, a trun line accessible .to said switch, another impulse transmitter and another automatic switch associated with said trunk line, means controlled by said irstimpulse transmitter for operating saidfirst automatic switch'to seize said trunk -linesaid second impulse transmitter automatically controlled by the seizure of said trunk line to operate said second automatic switch.

24.' lu a telephonesystem, ay calling and a called lino, a truuk line accessible to said calling line, an impulse transmitter associated with said trunk liuc, means :for extending a connection from the calling line to said trunk line, said impulse tranmnitter controlled by' the estabiishment of the connection with said trunk line to automatically extend said connection to the called line.

25. In a telephone system, an automatic switch, truuk lines accessible to said switch, an impulse transmitter associated with each trunk line, means for operating` said switch to select anidle one of said trunk lines, other automatic switches, and means controlled by the impulse transmitter associated with the selected trunk line for operating said other switches.

26 In a telephone'system,an automaticy switch, trunk lines accessible to said switch, an impulse transmitter associated witheach trunk line, means for operating; said switch to select an idle one of said trunk lines, other V automatic switches, and means controlled by the impulse transn'iitter associated with the selected truuk line for operating said switches in accordance vwith the digits of a called subscribers number.

Signed by me at Chioago'fCook county, illinois, this 19 day of August, 191A.

BERNARD D. WXLLSS. 

